1. Antibiotics
楊倍昌
Antibiotics and vaccines are among the biggest medical advances since (Culver Pictures)

2. A brief history of antibiotics
1495, mercury to treat syphilis.
1630, quinine (cinchona tree) for malarial fever by South American Indians.
1889, Buillemin defined antibiosis.
1910, Paul Ehrlich developed arsenical compound (Salvarsan) for syphilis, term: the chemical knife.
1929, Alexander Fleming found penicillin.
1935, Gerhard Domagk showed the value of sulfonamides.
1940, Ernst Chain and Howard Flory demonstrated the effect of penicillin.
, then searching for new antibiotics
~ recent year: modifying old drugs, finding new discipline in antibacterial combats
Early time in war: thanks penicillin, we can go home now
Now a day……….Oh eh?!

3. Thanks to work by Alexander Fleming ( ), Howard Florey ( ) and Ernst Chain ( ), penicillin was first produced on a large scale for human use in At this time, the development of a pill that could reliably kill bacteria was a remarkable development and many lives were saved during World War II because this medication was available.
E. Chain
H. Florey
A. Fleming

4. A tale by A. Fleming
He took a sample of the mold from the contaminated plate. He found that it was from the penicillium family, later specified as Penicillium notatum. Fleming presented his findings in 1929, but they raised little interest. He published a report on penicillin and its potential uses in the British Journal of Experimental Pathology.

5. Scenario of penicillin action on E. coli1 2 3 6 5 4
1: ordinary appearance
2-4: globular extrusions emerge
5: rabbit-ear forms
6: Ghost form

6. Evaluation by BUSINESS COMMUNICATIONS COMPANY, INC.,
year
By 2001, in developed countries, as many as 60% of hospital-acquired infections are caused by drug-resistant microbes. These infections are no longer found only in hospital or nursing home wards but are active in the community at large.

7. An ideal antibiotics Broad-spectrum Did not induce resistance
Selective toxicity, low side effects
Preserve normal microbial flora

8. Susceptibility test Tube dilution method Disk diffusion method
Minimal inhibitory concentration (MIC): the smallest amount of chemotherapeutic agent required to inhibit the growth of organism in vitro
Disk diffusion method
Zone of inhibition (ZOI): the correlation of ZOI and MIC has been established by FAD
ETest. This commercially-prepared strip creates a gradient of antibiotic concentration when placed on an agar plate

9. Guidance of antimicrobial therapy
Minimum inhibitory concentration: lowest concentration of antibiotic that inhibits visible growth (難用)
Minimum bactericidal concentration: lowest concentration of antibiotic that kills 99.9% of the inoculum
Serum bactericidal title: dilution of serum that kills 99.9% of the inoculum
Synergy test: synergistic activity of multiple antibiotics

10. In vitro: Factors for optimal antibiotic action
pH of environment:
Nitrofurantoin is more active in acid pH; sulfonamides and aminoglycoside are more active in alkaline pH.
Components of medium:
Anionic detergents inhibit aminoglycosides, serum proteins bind to penicillin in varying degrees.
Stability of drug:
Aminoglycosides and chloramphenicol are stable for long period in vivo.
Size of inoculums:
The larger the bacterial inoculum, the greater the chance for resistant mutant to emerge.
Metabolic activity of microorganisms:
Actively and rapidly growing organisms are more susceptible to drug action

11. Affecting factors in vivo
Abscess: circulation is blocked off.
Foreign bodies: obstruction of the urinary, biliary or respiratory tracts etc.
Immunity.

12. Sites of action

13. Modes of action (1)
Inhibitors of cell wall synthesis. Penicillins, cephalosporin, bacitracin, carbapenems and vancomycin.
Inhibitors of Cell Membrane. Polyenes - Amphotericin B, nystatin, and condicidin. Imidazole - Miconazole, ketoconazole and clotrimazole. Polymixin E and B.
Inhibitors of Protein Synthesis. Aminoglycosides - Streptomycin, gentamicin, neomycin and kanamycin. Tetracyclines - Chlortetracycline, oxytetracycline, doxycycline and minocycline. Erythromycin, lincomycin, chloramphenicol and clindamycin.
vancomycin
Amphotericin
Aminoglycosides
Tetracyclines

14. Modes of action (2)
Inhibitors of metabolites (Antimetabolites). Sulfonamides - Sulfanilamide, sulfadiazine silver and sulfamethoxazole. Trimethoprim, ethambutol, isoniazid.
Inhibitors of nucleic acids (DNA/RNA polymerase). Quinolones - Nalidixic acid, norfloxacin and ciprofloxacin. Rifamycin and flucytosine. 
rifamycin

15. Penicillin: an extensively studied example

16. Action mechanism of penicillin
Action target: cell wall
on penicillin binding proteins (PBPs)
Transpeptidases (form cross-links in peptidoglycan)
Beta-lactam ring attached to 5-membered thiazolidine ring
Accessibility of PBPs differ in gram+ and gram- bacteria
Amino acyl side chain groups determine spectrum, adsorption, susceptibility to lactamase
Bactericidal inhibitors

17. University of Maryland Biotechnology Institute (UMBI)
Resistance
Failure to bind to PBPs
Cannot penetrate porins (gram-)
Production of lactamase (penicillinase)
Lack autolytic enzyme
B-lactamase
Types:
Different substrate specificity
Penicillinases
cephalosporinases
Location:
Gram+: extracellularly
Gram-: periplasmic space
Metallo-b-Lactamase
Serine-b-Lactamase
By Dr. Osnat Herzberg
University of Maryland Biotechnology Institute (UMBI)

18. Drug resistance in general
Natural (inherent) resistance
Structural barrel
Lack of target
Transport system
Acquired resistance
Mutation
Gene exchange (conjugation in most)

19. Transferable antibiotic resistance in bacteria
Reduced uptake into cell (chloramphenicol)
Active efflux from cell (tetracycline)
Modification of antibiotic targets (b-lactam, erythromycin)
Inactivation of antibiotic by enzyme modification: hydrolysis (b-lactam, erythromycin); derivatization (aminoglycosides)
Sequestration of antibiotic by protein binding (b-lactam)
Metabolic bypass (sulfonamides)
Overproduction of antibiotic target (titration: sulfonamides)

20. Some probable overuse/misuse of antibiotics
Prophylactic use before surgery
Empiric use (blinded use)
Increased use of broad spectrum agents
Pediatric use for viral infections
Patients who do not complete course (chronic disease, e.g. TB, AIDS)
Antibiotics in animal feeds

21. Policy to deal drug resistance (1)
Ideally, bacteriological management of clinical infection should involve:
Identification of causative organism
Sensitivity test
Follow-up the drug effect
Monitor antibiotic level to avoid toxicity.
In reality, most patients requiring antimicrobial therapy are treated empirically. In serious infections immediate chemotherapy may be life-saving.

22. Policy to deal drug resistance (2)
Periodic changes of antibiotics used might change selective pressure and thus avoid the emergence of resistance and retain the therapeutic value of antibiotics over a longer period.
The unnecessary prophylactic or animal feeds use should be discouraged.
Distribution of information on current/updated infectious microbes (consult microbiologists): use more targeted antibiotics
Patient education (不隨便吃藥, 停藥)